Our project has four goals: (1) A socio-historical analysis of Mormon demography including the development of causal models to explain changes in major demographic parameters, (2) Application of the data base to the study of genetic demography and genetic structure of the population, (3) Synthesis of (1) and (2) to provide information necessary for population-based medical genetic research, and (4) Development of new methodology for the analysis of a large genealogical data base. Data are primarily derived from a set of family group sheets maintained by the Genealogical Society of Utah. A sample of 200,000 families, representing 1.2 million individuals, has been selected; these cover a period of about 150 years and include only those families which experienced at least one birth or death on the Mormon pioneer trail or in Utah. Our data base is being expanded with the addition of Utah death and birth certificates recorded since 1905. The population is of interest because it is well-defined and marked by migration, colonization, natural fertility, low mortality, and a forty-year period during which polygamy was practiced. Much of the methodology focuses on causual analysis of the relationships between demographic and socio-cultural phenomena. Basic demographic approaches (e.g., life tables, growth rates) and techniques from genetic demography (e.g., migration matrix analysis, calculation of effective population size) are employed. In addition, our unique data base system allows us to link large numbers of individuals in pedigrees so that results from the demographic and genetic analyses may be applied to problems in medical genetics.